We have recently pioneered the use of 15N-13C couplings in CNMR spectroscopy for studying the origin of carbon and nitrogen in secondary metabolism. The proposed research will examine the origin of streptothricin F using our 15N-13C coupling technique in order to 1) elucidate the primary precursors and the rearrangements that occur in the biosynthetic pathway, and 2) further define the scope and general applicability of our technique for studying complex problems in secondary nitrogen metabolism. We will also use a second heteronuclear coupling technique, that of 2H-13C couplings in CNMR spectroscopy, to help define certain mechanistic aspects. Streptothricin F, a metabolite of Streptomyces Lavendulae, is representative of a large group of broad spectrum antibiotics. Formed from at least three biogenetic building blocks, it is typical in complexity of the heterocyclic structures found in nature. In particular, it contains eight nitrogen atoms of certainly diverse origin. An understanding of the origins of nitrogen in secondary metabolites, as well as the metabolic lability of nitrogen in the natural precursors, has lagged far behind studies of secondary carbon metabolism due to the lack of suitable techniques.